Powered wheelchairs are commonly fitted with a tilt/lift arrangement which allows adjustment of the orientation and/or the height of the wheelchair seat. Such adjustment may be anterior, i.e. forward, or posterior, i.e. backwards tilting, and/or lifting of the seat. Commonly, tilting is referred to as the operation that affects the orientation of the seat while lifting affects the height of the seat. A seat occupant or caretaker may thereby for example set the seat position according to desire or current need of the occupant. Some examples of reasons for adjusting the seat position include achieving pressure relief, resting in general, the ability to better reach things or otherwise accommodate to the environment. Moreover, adjustment of the seat height and orientation may be a desirable feature for control purposes to stabilise the wheelchair depending on speed and travel on inclined surfaces.
An example of a wheelchair with tilt and lift capabilities is disclosed in EP2823796 A1. The powered wheelchair comprises a chassis frame, a lift device having a base member which is fixedly arranged to the chassis frame, and a lifting member arranged to move rectilinearly relative to the base member along an axis defined by a longitudinal extension of the lifting member, a tilt frame, a first arm pivotally coupled to the lifting member and the tilt frame, and a second arm coupled to the base member, and which second arm is pivotally coupled to the first arm forming a pivot connection, wherein movement of the lifting member towards the extended position moves the pivot connection towards the base member and movement of the lifting member towards the retracted position moves the pivot connection away from the base member.
US6447064 B1 discloses a wheelchair with a tiltable seat. The wheelchair has a tilt fulcrum between 3 and 7 inches from the front edge of the seat pan and between 1 and 4 inches below the surface of the seat pan. This minimizes the elevation of the rider's knees when in a tilted position, and allows for more stability and a shorter wheel base. Manual self-tilting is facilitated by a gas strut arrangement disposed on brackets below the seat pan, and operated by a rider-controlled valve.